Wheat producers should monitor fields closely for freeze injury

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MANHATTAN, Kan. – A hard freeze -- with temperatures well into the teens in western Kansas April 9 and expected again April 10 -- will almost certainly damage the wheat crop to some extent, said Jim Shroyer, K-State Research and Extension crop production specialist. Central and eastern Kansas also experienced freezing weather, but temperatures there were mostly in the upper 20s instead of the teens.

“The good news is that the wheat crop is not nearly as far along in development as it was at this time last year due to the drought, but any wheat at the jointing stage or later will probably lose some tillers where temperatures were in the teens for an extended time,” Shroyer said."

Where only some of the tillers have been damaged, there is still time for undamaged tillers to compensate and minimize any potential yield loss, but that will depend on having adequate moisture, which is uncertain this year, he added.

Wheat in the jointing stage can usually tolerate temperatures in the mid to upper 20s with no significant injury, Shroyer said. But, if temperatures fall into the low 20s or even lower for several hours, the lower stems, leaves, or developing head can sustain injury.

“If the leaves of tillers are yellowish when they emerge from the whorl, this indicates those tillers have been damaged. Existing leaves may also be damaged so severely that they turn bluish-black and water-soaked in appearance, then bleach out. This usually results in the field’s having a silage smell,” he said.

Wheat that hasn’t started to joint yet will probably suffer damage to the existing foliage, but the growing points will be protected by the soil and should escape injury, he added.

“This wheat will have cosmetic damage to the leaves that will show up almost immediately. If new leaves emerging over the next few weeks are green, that will indicate that the growing points survived and the plants will still produce tillers. If the new leaves are yellow, the growing point of that particular tiller was killed by the freeze,” Shroyer said. “The best thing producers can do for the first few days is walk the fields to observe lodging, crimped stems, and damaged leaves.”

“Be patient. Do not take any immediate actions as a result of the freeze, such as destroying the field for recropping. It will take several days of warm weather to accurately evaluate the extent of damage,” he said.

After several days, producers should split open some stems and check the developing head. If the head is green or light greenish in color and seems firm, it is probably fine. If the head is yellowish and mushy, it may have freeze injury.

Shroyer explained early signs producers might have noticed right away:

* Silage smell. If a wheat field is giving off the aroma of silage, it indicates that leaves have been damaged. Damaged leaves will likely turn black within a few days, then become bleached. If the flag leaf is killed, that tiller won’t produce much, if any, grain. Damage to lower leaves will not have such a drastic effect. Even if the flag leaf on the most advanced tillers is lost, less developed tillers can still come on and produce grain at this point in the season.

* Ice in the stems. If there was ice in the stems below the first node the morning of the freeze, those tillers will probably be damaged (although not always) and may not produce grain. When inspecting a field, flag the areas where you find ice in the stems, and tag individual tillers with suspected damage. Then come back to those areas after three days and see if the stems are crimped and damaged. If so, that tiller will probably not produce a head. If the tagged tillers continue to grow and put out nice green leaves, they are fine. If not, they probably had injury.

* Lodging. If the wheat lodged immediately after the freeze, that indicates stem damage. Later tillers may eventually cover the damaged tillers.

If the main tillers are injured, secondary tillers may begin growing normally and fill out the stand, Shroyer added.

“The wheat may look ragged because the main tillers are absent, but enough tillers may survive to produce good yields, if spring growing conditions are good. If both the main and secondary tillers are injured, the field may eventually have large areas that have a yellowish cast and reduced yield potential,” he said.

More information on freeze damage to wheat is available in “Spring Freeze Injury to Kansas Wheat,” K-State Research and Extension publication C646, available at county and district extension offices and on the Web at: http://www.ksre.ksu.edu/bookstore/ and type in C646 in the search function.


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